1. Field of the Invention
The invention relates to the field of ultrasonic (including megasonic) cleaning of substrate surfaces.
2. Description of Related Art
Removal of particulate contaminants from a semiconductor substrate can be accomplished by ultrasonic cleaning. When the frequency of ultrasound is close to or above 1,000 kHz (1 MHz) it is often referred to as “megasonic”.
Acoustically activated bubbles close to any liquid-surface interface causes (a) shear stress at the surface, which can lead to the removal of particulate contaminants from the surface, (b) microstreaming, which can lead to the enhancement of diffusion limited reactions beneficial for electrochemical deposition processes, etching, rinsing and mixing, and (c) local enrichment of active components close to the surface such as free radicals, ozone and plasma, to impact chemical processes such as oxidation processes and etching.
However, conventional ultrasonic and megasonic cleaning methods are not fully satisfactory as regards minimizing damage to the substrate during removal of nanoparticulate contamination, and avoiding cleaning patterns (i.e., non uniform removal).
There is therefore a need for treatment and cleaning technologies that effectively process or clean with minimal damage to the substrate.